Detector for a Linear Collider 8th Topical Seminar on Innovative Particle and Radiation Detectors Siena, 21 – 24 October 2002 Joachim Mnich RWTH Aachen

e + e – - Linear Collider Projects Physics at a 1 TeV e + e – - Linear Collider Implications for Detector Design Vertex Detector Tracking Detector Calorimeter Detector for a Linear Collider Outline:

Concepts for an e + e – - Linear Collider (  s = 500 GeV – 1 TeV) Cavities: superconductive normal Frequency: 1.3 GHz X- (11.4 GHz) or C-Band (5.7 GHz ) Route to higher energies (  s = 5 TeV): CLIC: Acceleration by Drive-Beam

A) cms-energy: TESLA-Project (DESY): Technical Design Report March MV/m   s = 800 GeV already achieved with improved manufacturing (electropolishing) Superconductive cavities Acceleration gradient 23 MV/m   s = 500 GeV

 800 GeV Very recent result from 4 nine-cell modules:

B) Luminosity Strong focussing at the interaction point Simulation Generation of small bunches: Final-Focus-Test (SLAC/DESY) Collision of bunches: Fast feedback system (Bunch separation: 337 ns) use beam deflection/widening after collision kicker magnets, Piezo-crystals

TESLA Electron-Positron-Collider Project:

Electron-Positron-Annihilation: Cross sections of SM- and MSSM-processes up to 1 TeV e + e –  ff   pb e + e –  HZ   10 fb (m H <<  s)  LC   LEP II /10 Luminosity: LEP II L = /cm 2 /s LC L  /cm 2 /s  Higgs-factory: 100/fb/year = 1000 HZ/year  Giga-Z (  s = m Z ) 10 9 Z-bosons in 1/2 year

Comparison of physics at LC and LHC LHC discovery machine for Higgs & SUSY LC precison measurements cf. discovery of W-and Z bosons at hadron collider then precision tests at LEP & SLC Physics at a 1 TeV e + e – - Linear Collider Keep in mind: Linear Collider comes probably after major discoveries at LHC Higgs physics Supersymmetry (SUSY) Alternative Theories Top-quark physics Standard Model (Giga-Z)...

Detection of Higgs Bosons independent of decay e + e –  H Z  H e + e – (  +  – )  Higgs branching ratios: Couplings to fermions: g f = m f /v Couplings to gauge bosons: g HWW = 2 m W 2 /v g HZZ = 2 m Z 2 /v  Determination of Higgs couplings: Higgs physics: Higgs-Strahlung

Spin: Energy scan at threshold (e.g. 3 points, 20 fb -1, 1/2 year) Determination of the quantum number of the Higgs: SM: J PC =0 ++ Parity: Angular distribution (continuum) Discriminate SM Higgs and 0 –+ -boson A

Verification of Higgs potential: H H H H H H H g HHH g HHHH Measurement of double Higgs strahlung e + e –  HHZ:  g HHH / g HHH = 0.22 Measurement of g HHHH not possible

Comparison of Higgs physics e + e – linear collider and LHC: m H = 120  160 GeV Linear collider will be in Higgs physics what LEP was in W- and Z-physics

Supersymmetry: If m SUSY < 2 TeV  discovery at the LHC Possible particle spectra: Advantage of Electron-Positron-Collider: Mass measurements by energy scans at kinematic threshold Polarisation of electrons (and possibly positrons) Separation of SUSY partners, e.g.: Skalar partners of fermions Fermionic partners of bosons  2 Higgs doublets SUSY will be new Standard Model

Detector R&D for an e + e – - Linear Collider: Higher particle energies from GeV to TeV More complex final states e + e –  ZHH  6 jets/leptons e + e –  H + H –  tb tb  8 jets Resolution e + e –  ZH  e + e – (  +  – ) + X SUSY (missing energy) Accelerator background, luminosity, bunch separation...we want to build the best apparatus... Why new & improved e + e – detector?

More differences to LEP Small cross section of signal  two-photon background Large Lorentz boost  high particle density in jets, e.g. 1/mm 2 in vertex detector Trigger: (example TESLA) bunch trains 1 ms, 5 Hz repetition rate bunch separation 337 ns but 199 ms between two trains 200 ms 1 ms  no hardware trigger No dead time Store data of whole train in front end Software selection within 200 ms

Detector R&D for an e + e – - Linear Collider: World wide R&D effort started Use most modern technology for best suited LC detector I. Vertex detectorIII. CalorimeterII. Tracker Here 3 examples:

I. Vertex detector Precise reconstruction of primary and secondary event vertices Identification of b- and c-quarks,  - leptons in Higgs decays  Multi-layer pixel detector TESLASLD Inner radius15 mm 28 mm Single point resolution < 5  m 8  m Material per layer (X 0 )0.06% X 0 0.4% X 0 Total material budget< 1% X 0 Impact Parameter 300  m for  > 3 (independent of  s) Goal: reconstruction of primary vertex  (IP) < 5  m  10  m / (p sin 3/2  ) SLD: 8  m  33  m / (p sin 3/2  )

1. Material budget: Thin detectors  60  m (= 0.06% X 0 ) Minimise support stretched silicon 3  m sagitta for 1.5 N tension Three main issues: Baseline design with 5 layers: Stand alone tracking Internal calibration

3. Readout speed: Integration of background during long bunch train small pixel size (20  m  20  m) to keep occupancy low read 10 times per train 50 MHz clock CCD design 2. Radiation hardness: High background from beam-strahlung and beam halo Much less critical than LHC But much more important than at LEP TESLA (r i = 1.5 cm) CMS (r i = 4.3 cm) Dose ( ,e –,h  ) 10 kGy1000 kGy Neutron flux10 10 /cm /cm 2

Vertex detector: Three technologies under consideration 1. Charge Coupled Device Create signal in 20  m active layer etching of bulk to keep total thickness  60  m 800 million pixels (SLD 300 million pixel) Coordinate precision 2-5  m Low power consumption (10 W) But very slow!  use column parallel readout CCD classic CP CCD

2. DEPFET (DEPleted Field Effect Transistor) Fully depleted sensor with integrated pre-amplifier Low power: 1 W/sensor Low noise: 10 e – at room temperature! Thinning to 50  m possible Result from a 64 × 64 pixel matrix: 50  m × 50  m pixel 9  m reolution To be shown: Column wise readout with 50 MHz 1987 (Kemmer,Lutz)

3. MAPS (CMOS Monolithic Active Pixel Detectors) Standard CMOS wafer, integrates all functions 1999 Same unique wafer for sensor and electronics i.e. no connections like bump bonds Very small pixel size achievable Radiation hardness proven Power consumption pulse power?

II. Tracker Study of Higgs production independent of Higgs decay  lepton momenta ideally: recoil mass resolution limited by Z width SUSY mass measurements - Pair production of scalar leptons (decay to lepton + neutralino) - Mass determination from end points of Momentum spectra Precise measurement of charged particle momenta:  Momentum resolution  (1/p t ) < 5 × (GeV/c ) -1 (full tracker)

Large Si-Tracker à la LHC experiments? much lower particle rates at linear collider keep material budget low  Large TPC 1.7 m radius 3% X 0 barrel (30% X 0 endcap) high magnetic field (4 Tesla) Goals: 200 points (3-dim.) per track 100  m single point resolution dE/dx 5% resolution 10 times better performance than at LEP

New concept for gas amplification at the end flanges: Replace proportional wires with Micro Pattern Gas Detectors - Finer dimensions - Two- dimensional symmetry (no E×B effects) - Only fast electron signal - Intrinsic ion feedback suppression GEM or Micromegas Wires GEM

Gas Electron Multiplier (GEM) (F. Sauli 1996) 140  m Ø 75  m 50  m capton foil, double sided copper coated 75  m holes, 140  m pitch GEM voltages up to 500 V yield 10 4 gas amplification Use GEM towers for safe operation, e.g. COMPASS

Micromegas (Y. Giomataris 1996) asymmetric parallel plate chamber with micromesh saturation of Townsend coefficient mild dependence of amplification on gap variations ion feedback suppression 50  m pitch

Disadvantage of electron signal: No signal broadening by induction Signal collected on one pad No centre-of-gravity Possible Solutions: Smaller pads Replace pads by bump bonds of pixel readout chips Capacitive or resistive coupling of adjacent pads Alternative pad geometries Strip couplingchevrons

III. Calorimeter Hermiticity to exploit missing energy signature of SUSY  No cracks Calorimeter inside magnet coils Fast readout & good time resolution to avoid event pile up Excellent energy and angular resolution - Mass reconstruction e.g. e + e –  t t - Distinguish hadronic W- and Z-decays e + e –  t t at threshold Goal for jet energy resolution

Jet energy resolution: W/Z identification by mass reconstruction in 4 jets: Include Fig from TDR

To get best jet energy resolution: measure every particle in the jet Energy distribution in typical multijet event: 60% charged particles  Tracker 30% photons  Ecal 10% neutral hadrons  Ecal + Hcal + good lepton ID Fine granularity (in 3 dim.) of electromagnetic and hadron calorimeters Combine tracks and clusters From energy flow to particle reconstruction!

Highly granular calorimeter: Electromagnetic: identify particles down to low energies longitudinal segmentation  X 0 X 0 / small transversal segmentation  r M no cracks, magnet coil outside Hadron calorimeter: cell size close to X 0 good cluster separation good energy resolution Si/W natural choice r M = 9 mm ECAL, HCAL with different absorbers and sampling  non compensating

But very expensive! particle Silicon-tungsten electromagnetic calorimeter: 1 cm 2 silicon pads 40 layers energy resolution  E/E < 0.1/  E/GeV  0.01

0.1 ATLAS CDF GLAST CMS NOMAD AMS01 CDF LEP DO Silicon Area (m²)  2000 m² Required silicon: 1 – 3  10 3 m 2 Price today: 5 $/cm 2

Alternative design for electromagnetic calorimeter: Tile fibre calorimeter (lead scintillator) Challenge: Fibre readout in 4 T field Optimize light yield of fibres Hadron calorimeter Use same design & components Coarser segmentation Compensation (lead/scint. 4/1) Use stainless steel ( ) Coarser granularity e.g. 5  5 cm 2

Digital hadron calorimeter Alternative design for hadron calorimeter: Highly segmented 1 cm 2 pads Binary readout per RPC or small wire chambers Simple frontend electronics

Precision measurements at Linear Collider  high demands on detector performance LEP/SLC like detector not sufficient Summary Flavour tagging H  cc Momentum resolution - e + e –  H Z  H e + e – (  +  – ) from lepton recoil mass - endpoint mass spectra in SUSY cascade Jet energy resolution - Higgs self-coupling HZZ - Multi-jet final states like ttH...

World wide R&D projects started: TPC Europe, US, Canada (TPC Working group alephwww.mppmu.mpg.de/~settles/tpc/welcome3.html) Calorimeter Europe, Asia, US ( CALICE coll. polyww.in2p3.fr/tesla/calice_offic.html) Much more R&D effort needed! International Linear Collider Detector R&D committee